When an optical beam from a light source such as a laser passes through a scattering medium such as biological tissue, random elastic scattering can distort and move the optical beam wavefront and any image of the optical beam on a target. Images produced by the optical beam are blurred by these distortions. The wavefront of the optical beam can be considered a surface passing through all points and having the same phase; the wavefront is generally perpendicular to the direction of propagation of the optical beam. The direction of propagation of the optical beam is also referred to as its optic axis.
One technique called adaptive optics has been developed to compensate for these distortions. In traditional adaptive optics, a wavefront sensor can be used to detect the wavefront of the optical beam, and a computer receives the output from the wavefront sensor and corrects for the distortions by reshaping a deformable mirror that lies in the path of the optical beam.